Brake cylinder pressure retaining and maintaining apparatus



Nov. 25, 1958 J. J. LIHOTA BRAKE CYLINDER PRESSURE RETAINING ANDMAINTAINING APPARATUS Original Filed May 29, 1951 18 i 4 Slow 16 i2 /25D recr Low 15 H iqh 'pi Pressure 2 Sheets-Shea- 1 Lou) Pressure SlowDireci' H iqh Pressur Direci High Press Pressure Direcr Direo 6Q 71 72'75 INVENTOR.

Joseph J Lz'hoia BY mum. a m

Nov. 25, 1958 J. J. LIHOTA 2,861,844

BRAKE CYLINDER PRESSURE RETAINING AND MAINTAINING APPARATUS OriginalFiled May 29, 1951 2 SheetsShee: 2

' High Pressure Low Pressure 120 f Direcr Direcf 47 41 42 rm H5INVENTOR. Jose 0h JLzlhoia BY ATTORNEY United States Patent 9 I BRAKECYLINDER PRESSURE RETAINING AND MAINTAINING APPARATUS Joseph'l, Lihota,Verna, Pa assignor to Westinghouse Air Brake Company, Wilmerding,Pa., acorporation of Pennsylvania Original application May 29, 1951, SerialNo. 223,850,

now Patent No. 2,760,830, dated August 28, 1956. Di-

vided and this a'pplicationOctoher 28, 1955, Serial No.

7 Claims. (Cl. 3034-75) .Thisinvention relates to fluid; pressure brakesand more particularly to means for retaining a chosen pressure of fluidin the brake cylinder devices on cars of a train while recharging thetrain brake system; this application b einga division of my copendingapplication, Serial No. 228,850,,"on which U. S. Patent 2,760,830 wasgranted on August 28, 1956. e

In order to ensure. safe control of railway trains while descending longgrades where one or more brake applications may'be required, manuallyadjustable retaining valve devices have long been employed on the carsto limit release of fluid under pressure from the brake cylinder deviceson the cars for thereby maintaining the car brakes applied with limitedforcewhile the brake pipe and associated apparatus of the brake systemare beingrecharged in preparation ,for a subsequent application ofbrakes. Leakage of fluid under pressure from abrake cylinder device willhowever defeat the purpose of a retaining valve device and the principalobject of the inventionis therefore the provision of improved means foroffsetting such leakage so as to thereby ensure that the pressure inthebrake cylinder device will remain at the desired selected reduceddegree.

Other objects and advantages will become apparent froin the followingmore detailed description of the invention.

In the accompanying drawings; Fig; 1 is a diagrammatic view of a fluidpressure brake apparatus for a car embodying one form of the invention;Fig. 2 is a diagrammatic, development view of a valve constituting apart of Fig. 1;.and Figs. 3, 4 and 5, .6 are, views similar to Figs. 1and 2, respectively; of different embodiments of the invention.

Description-Figs. 1 and 2 As shown inFig. .1, the reference numeral 1designates a brake controlling valve device of any conventional typewhich is adaptedtto respond to. a reduction in pres sure in. a brake.pipe 2 to supply fluid under pressure from asource of fluid underpressure such as may be present in an-auxiliary reservoir 3 tothepressure ehamber 4. of a brake cylinder device 5. In chamber 4 thepressure of fluidwill act on a brake cylinder piston 6 to move saidpiston againstarelease spring 7 to apply brakes on a car, as well-known.Upon recharging the brake pipe 2 with fluid under pressure, the brakecontrolling valvedev ice 1 will' operate in the usual well-known mannerto rechar'gethe auxiliary reservoir 3 with fluid under pressurefrornsaid brake pipe and at the same'time open the brake cylinderpressure chamber 4 through a cavity, 8 in a slide-valve 9 of said deviceto a retainer pipe 10 for releasing fluid underpressure from saidchamber either completely or partially-dependent upon the adjustment ofa pressure retaining; valve device 11.

For illustration, the pressure retaining valve device 11' maybe likethatdisclosed in Patent No. 2,204,796 issued on :1 unc 18", #1940 to -C.C. Farmer.

2,861,844 Patented Nov. 25,1958

retaining valve device 11 comprises a, casing containing low and highpressure retaining, check valvesf12', 13, respectively, and a plug valve14 which {is rotatable manually by a handle 15 to four differentpositions im dicated by lines to which areapplied the legends Direct,High Pressure, Low Pressure and Slow Direct, respectively.

The low pressure check valve 12 is contained in a chamber 16 andi'sarranged to control co'mn'runicatiQn between said chamber and a chamber17 towhich the retaining pipe 10 is connected, a spring 18 in chamber'16acting on said valve urging it toward i'ts seat 'with chosen force-such,for-example, as to require fluid at a. pressure in chamber 17-ten poundshigher than that in chamber 16 to open or-unseat said check valve.

The high pressure check valve 13 contained in a chainber 19 isprovidedto control-communication between said chamber. and a chamber 20and. is urged to its seat by a spring 21 in chamber 19 with a forcewhichmaybe the same as that of spring 18 on the low pressurecheck valve 12.Chamber 20 is open through a choke 22 to chamber 16and chamber 19 isopen through a choke 23 to a passage 24leading to one side of the plugvalve 14.

Also opening to the, side of the plug: valve. 14.; are chambers 17 and20, an atmospheric exhaust port,25

and one end of a restricted passageway 26 the. opposite end of which isopen to chamber 17.

Now assume that subsequent .to effecting an application of brakes bysupplyingfluid under pressure to chamher 4 in the brake cylinder device5, the parts of the triple valve device 1 have been movedback toreleaseposition for. recharging the auxiliary reservoir 3 and i for openingsaid chamber to the retaining. pipe. ltland thence in said valve willconnect passageway 27 to the exhaust passage 25, whereupon fluid underpressure from the re},- taining pipe 10 present in chamber 17 willliftthe check valve. 12 and flow to chamber 16 and thence to chamber 20wherein it will act to unseat the check valve 13 and flow to chamber 19and thence to atmosphere via passage 24, passageways, 28 in the plugvalve 14 aiid the exhaust port 25. Thus, inthe high pressure position ofhandle 15, fluid under pressure will be released from the brake cylinderpressure chamber 4 until the pres sure retained insaid pressure chamberwill be equal to the combined pressures of springs 18, 21 on the respective check valves .12, 13 or, .for example, twenty pounds.

If the handle 15;is inthe Low Pressure position, passageway 27 in theplug valve 14'will open chamber 20 directly to the exhaust port 25;whereupon fluidTs leased past the low pressure check valve 12 willescape directly to atmosphere end such will gontinue until the pressurein the brake. cylinder. pressure chamber-419ecomes reduced to a degree,such as ten pounds, which is insuflicient to unseat'the check valve 12,whereby'the pressure of fluid retained in the brake cylinder pres' tion,the retainer pipe 10 will be open directly to at'riiesphere throughchamber 17, the restricted passageway 26,

passageway 27 in the plug valve 14 and theexhausi port 25 wherebycomplete release of fluid under pressure from the brake cylinderpressure chamber 4 will occur but at a slower rate than in the Directposition.

The structure and operation of the structure so far described iswell-known. It is however to be noted that if there should be leakage offluid under pressure from the brake cylinder pressure chamber 4 past thepiston 6. the pressure in said chamber will undesirably reduce afterclosing of the valves 12, 13 in the High Pressure or Low Pressurepositions of the retainer valve handle 15 and such is undesirable sincea brake application may become completely released or reduced either ofwhich is undesirable from the standpoint of safety of a train. Theinvention, which'will now be described, provides for maintaining thepressure in the brake cylinder pressure chamber 4 at the pressurecorresponding to the High Pressure position or Low Pressure position ofhandle 15 while recharging the brake system on a car or train of cars.

According to the invention, as shown in Figs. 1 and 2, I-associate withthe brake apparatus, so far described, a pressure maintaining valvedevice 30 and a selector valve device 31.

The valve device 30 comprises a supply valve device 32, a low pressuremaintaining valve device 33 and a high pressure maintaining valve device34.

The supply valve device 32 comprises a supply valve 35 contained in achamber 36 which is adapted to be constantl'y supplied with fluid underpressure from any suitable source, such as the auxiliary reservoir 3,via a pipe 37 in which there is placed a choke or restriction 38. Thevalve 35 is provided for controlling flow of fluid under pressure fromchamber 36 to two chambers 39 and 40 via a connecting passage 41 and isurged to a closed position by a spring 42 for preventing such flow. Astem 43 slidably mounted in a suitable bore in the casing .of the devicehas one end engaging the seating side of valve 35 while the opposite endterminates in a follower head 44 engaging one side of a flexiblediaphragm 45 in a chamber 46 at one side ,of the diaphragm. Chamber 46is open 'to atmosphere through a port 47. At the opposite side ofdiaphragm 45 is a control chamber 48 open to a pipe 49 leading to theselector valve device 31; Upon supply of fluid under pressure to chamber48 {as will be later described) the diaphragm 45 is adaptedto deflect tooperate stem 43 to open valve 35 for supplying fluid under pressure tochambers 39 and 40, while upon release of fluid under pressure fromchamber 48 spring 42 is adapted to close valve 35.

The low pressure maintaining valve device 33 comprises a maintainingcheck valve 50 contained in chamber 39 for controlling communicationbetween said chamber and a chamber 51 opento a pipe 52 leading to theselector valve device 31; a spring 53 in chamber 39 acting spring 58acting on the diaphragm with such force as to deflectfit to unseat valve50 when opposing pressure of fluid in chamber 51 in just slightly lessthan that (ten pounds) at which the check valve 12 seats in the Lowcheck valves 12 and 13 seat in the High Pressure position of theretaining valve handle 15. The valve 59 is provided to control flow offluid under pressure from chamber 40 to chamber 64 which is connected toa pipe 65 leading to the selector valve device 31. At the opposite sideof diaphragm 61 is a chamber 66 containing spring 63 and open toatmosphere through a vent 67.

The selector valve device 31 comprises a casing to which the pipes 10,49, 52 and 65 are connected and a plug valve 68 mountedin said casingand arranged to turn with the plug valve 14 in the retaining valvedevice 11. In practice the plug valves 68 and 14 may, if

' desired, be one and the same valve.

Pressure position of the retaining valve handle 15. The

chamber 40, a flexible diaphragm 61 connected to valve I 59 through astem 62 and a spring 63 acting on said diaphragmfor unseating said valvewhen pressure of fluidin a chamber 64 at one side of said diaphragm isjust slightlyless than that (twenty pounds) at which both In the Directposition of the retaining valve handle 15 in which the retainer pipe 10is open directlyto atmosphere through the relatively large passageway 27to provide normal rate of release of fluid under pressure from the brakecylinder device 5, the connections of pipes 10, 52 and 65 to theselector valve device may be closed by the plug valve 68 while pipe 49may be vented to atmosphere through a cavity 69 in the plug valve 68 andan exhaust port 70 in the casing thereof (Fig. 2). With pipe 49 andthereby diaphragm chamber 48 vented the supply valve 35 Wlllbe seated byspring 42 so that there can be no flow of fluid under pressure from themaintaining valve device 30 to pipe 10. I

.Now assume that the retaining valve handle 15 is in High Pressureposition at the time of releasing fluid under pressure from chamber 4 inthe brake cylinder device 5. In this position both check valves 12, 13in the retaining valve device will seat when the pressure in the brakecylinder chamber 5 is reduced to a chosen degree such as twenty pounds.In this position of handle 15 and thereby of plug valve 68 of theselector valve device a cavity 71 (Fig. 2) in the plug valve opens theretaining pipe 10 to pipes 49, 65 whereby brake cylinder pressure willbecome effective in diaphragm chambers 48, 64 of maintaining valvedevice 30. If brake cylinder pressure chamber 4 is then charged withfluid under pressure, pressure of such fluid thus provided in chamber 48will deflect diaphragm 45 to open valve 35 for thereby supplying fluidunder pressure from the source (auxiliary reservoir 3) to valve chamber40, while brake cylinder pressure in chamber 64 will deflect diaphragm61 .against spring 63 to permit closing of valve 59 by spring 60 as- Thecheck valve 59 may be unseated, as just described,

just suflicient to permit such flow of fluid under pressure to brakecylinder pressure chamber 4 as to compensate for the leakage, in whichcase it will remain open as long as retaining valve handle 15 is in theHigh Pressure position. On the other hand, when the valve 59 is openedinertia may cause it to open to a greater extent, in which case, fluidunder pressure will be supplied to chamber 64 at a rate greater thannecessary to compensate for leakage.

fleet said diaphragm to permit closing of said valve.

Leakage will then again reduce the pressure in chamber 64 in response towhich the valve 59 will again be opens and closes or obtains apositionupon opening to just' compensate for leakage for, frompractical'standpoint, thepressure ;in thebrake cylinder pressurechamberg4; will remain substantially at the pressure .corre-i Thepressure in chamber 64' will then increase to a degree slightly greaterthan theopposing pressure of spring 63 on diaphragm 61 ,and despendingto the High Pressure position 'of-handledS.

if retaining valve handle '15 should be in .Low Pressure position at thetime the charged brake cylinder pressure chamber 4 is opened toretainer, pipe 10,11 cavity 72 in the plug valve 68 will open pipe topipes 52 and 49, whereby the supply valve 35 will be opened to supplyfluid under pressure to valve chamber 39 and the low pressuremaintaining valve device 33 will then operate the same as the highpressure maintaining valve device 34 operated, as above described, in'case of leakage of fluid under pressure from the brake cylinderpressurcchamber 4 to maintain the pressure therein substantially equal to that(ten pounds) present at the time ofcseating of the check valve 12 in theretaining valve device, as will be evident without detailed description.

It handle should be in the Slow Direct position at the time ofconnecting the charged brake cylinder pressure chamber 4 to the retainerpipe 10,.the plug valve 68 will lap pipes ltl, 65 and 52 and vent pipe49 via cavity 73 therein so as to prevent operation of the maintainingvalve device 30, the same as in the Direct position of handle 15.

It will now be seen that in the Low Pressure and High Pressure positionof handle 15, retaining valve device 11 will operate in the usual mannerto permit reduction in pressure in the charged brake cylinder pressurechamber 4 to the respective reduced degree, andtthat in case of leakageof fluid under pressure from said chamber, the pressure therein will bemaintained against leakage substantially at the desired reduced degree.by the maintaining valve device 3t). In the Direct and Slow Directpositions of handle 15 the maintaining valve device 30 will be cut outof operation attimes,

it will be noted, when retention of a certain pressure in the brakecylinder pressure chamber 4 is not desired.

Description-Figs 3 and 4 If desired, the functions of the usual pressureretaining valve device 11 andpressure maintaining valve device 30 shownin Fig. 1, may be combined intota single retaining and maintaining valvedevice 75, shown .iniFig. 3, arranged to be controlled by a selectorvalve device 76.

The valve device 75 comprises a supply valve device 77, a low pressureretaining and maintaining valve device 78 and a high pressure retainingand maintaining valve device 79 and is like the maintaining valve device30 shown in Fig. 1 except for the addition of retaining check valves 80and 81 arranged for control by diaphragms 54, 61 of the valve devices78, 79, respectively. Accordingly, the same reference numerals have beenapplied to corresponding parts in the two devices 30-, 75.

The check valve 80 is contained in a chamber 82 open to pipe 52, and aspring 83 in said chamber is provided to seat said checkvalve whichcontrols communication between said chamber and the atmospheric chamber56. A stem 84 contained in chamber 56 with one end connected todiaphragm 54 has itsopposite end disposed for engagement with theseating side of check valve 80 for unseating same by deflection of saiddiaphragm after the check valve 50 is seated. Similarly, the check valve81 is contained in a chamber 85 open to pipe '65, and a spring 86 insaid chamber is provided to seat said valve for closing communicationfrom said chamberto the atmospheric chamber 66. A stem 87 in chamber 66connected at one end to diaphragm 61 is provided to contact the checkvalve 81 and unseat same by deflection of; saiddiaphragm after thecheckvalve 59 is seated.

The selector valve device 76 comprises a casing to which are connectedpipes 10, 49, 52 and 65, like the selector valve device 31, and whichcontains a plug valve 8-8. 1 A handle 39 lravingthe same positions asthe"retaining valve handle 15 'of Fig: lis connected to plug'valve 88 forturningit to corresponding positions. The-plug 6 valve 88 has the samecavities 69; 71, 72 and 73 (Fig. 4) as the plug valve 68 and in additioncavities 90, 91 open to cavities 69 and 73, respectively, thecommunication between cavities 91 and 73 including a choke 92 forperforming the function of the restricted passageway 26 in the retainingvalve device 11 of Fig. 1.

In operation, if selector valve handle 89 is in Direct position at thetime fluid under pressure is released from the brake cylinder pressurechamber 4 to pipe 10, fluid under pressure will flow directly toatmosphere through cavities and 69 in the, plug valve 88 and exhaustport 74 pipes 65 and 52 being lapped by said valve, and pipe 49 beingvented the same as in the structure shown in Fig. 1.

If the selector valve handle 89 is in the High Pressure position whenfluid under pressure is released from the brake cylinder pressurechamber 4 to pipe 10, such. fluid will flow through cavity 71 in theplug valve 88 to pipes 65 and 49. The supply valve device 77 willthereby be operated to open supply valve 35 to supply fluid underpressure to the valve chamber 46; and at the same time brake cylinderpressure from pipe 65 becoming effective in chamber 64 On diaphragm 61of the high pressure valve device 79 will deflect said diaphragm againstspring 63 to open valve 81. With the valve 81 thus open fluid underpressure will be vented from the brake cylinder device and diaphragmchamber 66 to atmosphere via chamber 66 and vent 67 until such pressurebecomes reduced to the chosen degree, such as twenty pounds, .at whichspring 63 will deflect diaphragm 61 downward to permit spring 86 to seatvalve 81 for thereby terminating release of fluid under pressure fromthev brake cylinder chamber 4. If now there is leakage of fluid underpres sure from the brake cylinder pressure chamber 4, the resultantreduction in pressure in chamber 64- will cause the diaphragm 6i to openthe supply valve 59 to supply fluid under pressure to said chamber tocompensate for such leakage, the same is in the structure shown in Fig.1.

If selector handle 89 is in Low Pressure position at the time thecharged brake cylinder pressure chamber. a is opened. to pipe 10, saidpipe will be opened by cavity 72 in the selector valve 88 to pipes 52and 49 whereby the supply valve 35 will be opened and the low pressurevalve device 73 will be operated to permit release offluid underpressure from said chamber via valve 89 until such pressure is reducedsufficiently to permit deflection of diaphragm 5 5 by spring 58 andthereby closure of valve 80, and finally in case, of leakage of fluidunder pressure from the brake cylinder chamber 4, opening of valve 50 tocompensate for leakage, as will be readily apparent from previousdescription.

If selector handle 89 is in Slow Direct position when the charged brakecylinder pressure chamber 4 is opened to pipe 10, fluid under pressurewill be vented from said chamber via cavity 91 in the plug valve, choke92, cavity 73 and exhaust port 70, while pipes 65 and 52 will be lappedby said valve and pipe 49 will also be vented by way of exhaust port 70,so that the valve device 75 will not operate to either limit release offluid under pressure from the brake cylinder device or to supplyfluidunder pressure thereto, thereby providing the same result as thestructure of Fig. 1 provides in the corresponding position of handle.

It will now be seen that the valve device 75 of Fig. 3 will provide thesame result as the retaining valve device 11 and valve device 30 of Fig.1.

Descriptionmg. 5 and 6 It desired, the retaining valve device 11 of Fig.1 may be dispensed with and the function thereof embodied in a'retainingcheck valve 114 of a combined retaining and maintaining valve device 115shown in Fig. 5. The device115 comprises a supply valvedevice and a maintaiiiingvalvedevice 116.

The supply valve device 95 may be the same in structure and operation asthe supply valve devices 32 and 77 previously described, and the samereference numerals have therefore been applied to like parts.

The maintaining valve device 116 comprises a maintaining check valve 96contained in a chamber 97 open to passage 41 and thusadapted to besupplied with fluid under pressure when valve 35 is open. A spring 98acts on valve 96 to urge it seated. A stem 117 at one end engages theseating face of valve 96 for unseating it. The stem 117 extends into achamber 100 at one side of a flexible diaphragm 101, at the oppositeside of which is a chamber 102 open to atmosphere through a vent 103.The stem 117 at the opposite end has the valve 114 which is arranged toopen and close communication between chamber 100 and a passageway 119opening through diaphragm 101 to atmospheric chamber 102. The chamber100 and chamber 48 in the supply valve device 95 are both connected to apipe 104 leading to a selector valve device 120. In chamber 102 acontrol spring 106 has one end bearing on the diaphragm 101 while theother end bears against a plunger 107 slidably mounted in a suitableboi'e in the casing of the device. By adjustment of plunger 107 in itsbore the pressure of spring 106 on diaphragm 101 may be varied.

For adjusting the position of plunger 107 in its bore a cam 108 isprovided for operation by a handle 122, similar to handle 89. Theperipheral surface of cam 108 engages the plunger 107 and is so designedas to vary the displacement of plunger 107 against spring 106 andtherefore the pressure of said spring against diaphragm 101 inproportion to the extent of movement of handle 122 from the HighPressure position to the Low Pressure position, or vice versa, providingmaximum displacement in the High Pressure position and minimum displaceany desired position between the High Pressure and- Low Pressureposition. The plug valve 121 is provided with a cavity 123 for, in theDirect position of handle 122, opening pipe directly to atmosphere viaan exhaust port 124 (Fig. 6) to provide for usual release of fluid underpressure from the brake cylinder pressure chamber 4. Pipe 104 is alsovented in this position via cavity 123 so that the supply valve 35 willbe closed. The plug valve 121 also has a cavity 125 which in the SlowDirect position of handle will vent both pipes 10 and 104 via exhaustport 124, but a choke 126 is placed in said cavity to restrict exhaustfrom the retainer pipe 10 (but not from pipe 104) so as to provide forthe slow release of fluid under pressure from the brake cylinderpressure chamber 4 like provided by the restricted passage 26 in theretainer valve device 11 (Fig. 1).

10 and 104 in the High Pressure and Low Pressure positions and allintermediate positions of handle 122.

In operation, if handle 122 should be in the High Pressure position whenthe charged brake cylinder pressure chamber 4 is connected to pipe 10,pressure of fluid from said chamber will become effective in chamber 48to open the supply valve 35, and at the same time such pressure becomingeflective in chamber 100 will deflect diaphragm 101 to permit seating ofvalve 96 by spring 98 and opening of the release valve 114. Fluid underpressure will then be released from the brake cylinder pressure chamber4 past release valve 114 until reduced to a chosen pressure at whichspring 106 will deflect diaphragm 101 into. seating engagement with therelease valve 114. If leakage from the brake cylinder pressure chamber 4then continues to reduce the pressure therein The plug valve 122 alsohas a cavity 113 for connecting pipes to deflect diaphragm 101 to openvalve 96 for supplying fluid under pressure to said chambers tocompensate for such leakage. I

If the handle 122 should be in Low Pressure position at the time thecharged brake cylinder pressure chamber 4 is connected to pipe 10 anddiaphragm chamber 100, the pressure of fluid in said chambers will bereduced past the release valve 114 to the chosen degree determined bythe cam adjustment of spring 106; whereupon said valve will be closed,and in case of leakage of fluid under pressure from said chambers, thediaphragm 101 will then operate to open the valve 96 for supplying fluidunder pressure to said chambers to compensate for leakage.

Since the cam 108 is designed to vary the pressure of spring 106 ondiaphragm 114 according to the position of handle 122 between the HighPressure and Low- Pressure positions, if said handle should be in anyposition intermediate said positions the release valve 114 will beclosed at a corresponding different pressure and, in case of leakage, itwill be compensated for in a manner which will be apparent from theabove description. The ability to thus retain any one of a number ofdifferent pressures in the brake cylinder pressure chamber 4 isdesirable in that it not only provides for adjustment of handle 122according to a grade being descended but also according to the weight ofa car or the load carried by the car.

Operation of the novel arrangements constituting the three embodimentsof the invention have now been de scribed under conditions where thehandles 15, 89 and 122 are already assumed to be in their respectiverecited positions. It is to be noted, however, that according to afeature of the invention, if handle 15, 89, or 122 is moved from itsrespective Direct or Slow Direct position to either its High Pressure orLow Pressure position while 'brakes are released and the brake cylinderpressure chamber 4 is consequently vented, the chamber 48 of therespective supply valve devices 32, 77, will remain vented and hence thecorresponding supply valve 35 will not be unseated. Hence, the handle15, 89 or 122. may be set while the train is on level terrain, withbrakes released, at the "bottom of a mountain before the ascent; thisbeing especially desirable when there is a tunnel or dangerous terrainat the crest of the mountain. Brake cylinder pressure will be retainedand maintained according to the selected setting of the valve handle 15,

89 or 122 during and after release of the first brake applicationfollowing movement of such handle to High Pressure or Low Pressureposition (and in the case of handle 122 to any other positionintermediate said High 1 Pressure and Low Pressure positions). By way ofcontrast, with brake cylinder retaining and maintaining arrangementspreviously proposed, as soon as the handle is set to maintain brakecylinder pressure at a certain value, fluid under pressure will beimmediately supplied from the maintaining source to the brake cylinderdevice and apply brakes to a degree corresponding to the brake cylinderpressure desired to'be retained, if brakes are not ing pipe 37 directlyto the chambers 39, 40 (Figs. 1 and 3) or chamber 97 (Fig. 5).

Summary Itiwill now be seen that Ihave provided means for holdingpressure in the brake cylinder device on a car at a selecteddegreeagainst leakage while recharging the brake apparatus :on the earand. hence in a train of, such cars to betterfacilitate safe descent-ofa -grade. The vention may constitute a device adapted to beassociatedwiththe usual pressureretaining valve device and therefore requiringonly the function of maintaining or, if desired, it may also embodytheblow-down function of the usual retaining valve device. Moreover, ifdesired, the device maybe of a form to maintain the pressure in thebrake cylinder'device at any desiredone of an infinite number ofdifferent pressures.

Having now described the invention, what I claim as new and desire tosecure by Letters=Patent, is:

1. Means for controlling pressure of fluid in the retainer pipe of afluid pressure brakeuapparatus'having a brake cylinderdevice which isadapted to beopene'd to said retainer pipe for eflecting a-release ofbrakes, said means comprising supply valve means, responsiveto supply offluid under pressure to one chamber to supply fluid under pressure toanother chamberand responsive to release of fluid under pressure fromsaid one chamber to cut off supply of fluid under pressure to said otherchamber, a normally seated retaining check valve controlling release offluid under pressure from adifferent chamber, a normally seatedmaintaining check valve controlling supply of fluid under pressure fromsaid other chamber to said different chamber, a spring, movable abutmentmeans controlled by pressure of said spring opposing pressure of fluidin said different chamber and operative to unseat said retaining checkvalve to effect release of fluid under pressure from said differentchamber to a value corresponding to the pressure of said spring andoperative to unseat said maintaining check valve to effect supply offluid under pressure from said other chamber to said different chamberas required to balance the pressure of said spring, andoperator-controlled valve means for either opening said retainer pipe tosaid one and different chambers or for venting said one and differentchambers and retainer pipe directly to atmosphere.

2. Means for controlling pressure of fluid in the retainer pipe of afluid pressure brake apparatus having a brake cylinder device which isadapted to be opened to said retainer pipe for effecting a release ofbrakes, said means comprising a control spring, movable abutment meanssubject to pressure of said spring opposing pres sure of fluid in achamber, valve means controlled by said movable abutment means forreleasing fluid under pressure from and supplying fluid under pressureto said chamber as required to balance the pressure of said spring,other valve means for opening said retainer pipe to said chamber or toatmosphere, cam means for varying pres sure of said spring on saidmovable abutment means, and a lever for concurrently controllingoperation of said other valve means and cam means.

3. In a fluid pressure brake apparatus for a railway car, thecombination of a brake pipe, brake means operable by fluid underpressure to effect an application of brakes and responsive to release ofsuch fluid under pres sure to eflect a release of brakes, a retainerpipe, brake controlling means responsive to a reduction in brake pipepressure to supply fluid under pressure to said brake means andresponsive to a subsequent increase in brake pipe pressure to open saidbrake means to said retainer pipe, retaining and maintaining meanscomprising retaining valve means for releasing fluid under pressure fromsaid retainer pipe, maintaining valve means for supplying fluid underpressure to said retainer pipe, a lever, and means operable by movementof said lever to various positions for providing concurrent control overoperation of said retaining valve means and maintaining valve means, thelast mentioned means being effective in some of said positions of saidlever to cause said retaining valve means to effect release of fluidunder pressure from said retainer pipe to different chosen values aboveatmosphere and also cause said maintaining valve means to concurreutlylimit the pressure of fluid which will be supplied to saidretainerpipeto substantially the respective chosen value then effective,and other value means controlled by said lever and operablein saidsomepositions of the lever to connect the retainer pipe to said retainingvalve means and maintaining valve means operative in another position ofsaid lever to open said retainerpipe to atmosphere in by-pass of saidretaining valve'means and maintaining valve means.

4. Meansfor controlling pressure of fluid in the retainer pipe of afluid pressure brake apparatus having a brake cylinder device which isadapted to be opened to said retainer pipe for effecting a release ofbrakes, said means comprising operator-controlled valve means forselectively connecting the retainer pipe to a chamber or to atmospherein by-pass of said chamber, a retaining check valve for controllingrelease of fluid under pressure from said chamber to atmosphere,'amaintaining check valve for controlling supply of fluid under pressureto said chamber, resilient means, a movable abutment interposed betweenand arranged coaxially with said re taining check valve and saidmaintaining check valve, a pair of stems arranged at opposite sides ofand coaxially with said movable abutment forcontrolling opening of saidretaining check valve and maintaining check valve selectively by saidmovable abutment, said movable abutment being controlled by pressure offluid. in said chamber opposing pressure of said resilient means andoperative to open said retaining check valve or said maintaining checkvalve through the medium of a corresponding one of said stems accordingto whether pressure in said chamber exceeds or is less than a chosenvalue corresponding to the pressure of said resilient means, thereby toprovide in said chamber fluid at substantially said chosen value ofpressure.

5. Means for controlling pressure of fluid in the retainer pipe of afluid pressure brake apparatus having a brake cylinder device which isadapted to be opened to said retainer pipe for effecting a release ofbrakes, said means comprising supply valve means responsive to pressureof fluid in one chamber to supply fluid under pressure to anotherchamber and to venting of said one chamber to cut off such supply,retaining valve means controlling fluid pressure connection of adifferent chamber to atmosphere, maintaining valve means controllingfluid pressure connection of said other chamber to said differentchamber, resilient means, fluid pressure motor means controlling both ofsaid fluid pressure connections, said motor means being subject toopposing pressures of fluid in said different chamber and of saidresilient means and operative to cause opening of one or the other ofsaid fluid pressure connections according to Whether pressure in saiddifferent chamber exceeds or is less than a chosen valve correspondingto the pressure of said resilient means and to cause closure of both ofsaid connections when pressure in said diflerent chamber issubstantially equal to said chosen value of pressure, andoperator-controlled valve means for selectively connecting the retainerpipe to said one chamber and different chamber or connecting theretainer pipe to atmosphere in bypass of said one and differentchambers.

6. In a fluid pressure brake apparatus for a railway car, thecombination of brake means operable by fluid under pressure to effect anapplication of brakes and responsive to release of such fluid underpressure to effect a release of brakes, a brake pipe, a retainer pipe,an auxiliary reservoir, brake control means responsive to a reduction inbrake pipe pressure to supply fluid under pressure from said auxiliaryreservoir to said brake means and responsive to a subsequent increase inbrake pipe pressure to prevent such supply from said auxiliary reservoirto said brake means and open the latter to said re tainer pipe, supplyvalve means responsive to pressure of fluid in one chamber to effectsupply of fluid under pressurefrom said auxiliary reservoir to anotherchamber and responsive to venting of said one chamber to terminate suchsupply of fluid under pressure to said other chamber, retaining valvemeans for controlling release of fluid underlpreissure from a differentchamber, maintaining valve means controlling supply of fluid underpressure to said different chamber from said other chamher, controlspring means, movable abutment means subject opposingly to pressure offluid in said different chamber and pressure of said control springmeans for so controlling selective opening of said retaining andmaintaining valve means as to normally provide in said different chamberfluid at a pressure required to balance the pressure of said controlspring means, and selector means operable in one position to-open saidone and different chambers to said retainer pipe and in another positionto open said retainer pipe and one and different chambers to atmosphere.

77 In a fluid pressure brake apparatus for a railway car, thecombination of brake means operable by fluid under pressure to eifect anapplication of brakes and responsive to release of such fluid underpressure to effect a release of brakes, a brake pipe, a retainer pipe,brake control means responsive to a reduction in brake pipe pressure tosupply fluid under pressure to said brake means and responsive to asubsequent increase in brake pipe pressure to open'said brake means tosaid retainer pipe,-supply valve means responsive to pressure of fluidin one chamber to eifect supply of fluid under pressure to anotherchamber and responsive to venting of said one 12 chamber to terminatesuch supply of fluid under pressure to said other chamber, retainingvalve means for vcontrolling release of fluid under pressure from adifierent chamber, maintaining valve means controlling supply of fluidunder pressure to said different chamber from said other chamber,control spring means, movable abutment means subject opposingly topressure of fluid in said diiferent chamber and pressure of said controlspring means for so controlling selective opening of said'retaining andmaintaining valve means as to normally provide in said different chamberfluid at a pressure required to balance the pressure of said controlspring means, cam means for adjusting the pressure of said controlspring means, selector valve means operative in some positions to openthe retainer pipe only to said one and different chambers and in otherpositions to open the retainer pipe and said one and diiferent chambersto atmosphere, and an operators control lever for concur-i rentlycontrolling operation of said cam means and selector valve means.

References Cited in the file of this patent UNITED STATES PATENTS1,012,720 Sauvage Dec. 26, 1911 1,447,791 Kummerow Mar. 6, 19231,892,261 Wilson Dec. 27, 1932

